Neuropathic Pain Flashcards
Neuropathic Pain
Neuropathic pain may be defined as pain which arises following damage or disruption of the nervous system. It is often difficult to treat and responds poorly to standard analgesia.
Neuropathic Pain - Examples
Examples include: diabetic neuropathy post-herpetic neuralgia trigeminal neuralgia prolapsed intervertebral disc
Neuropathic Pain - Mx
NICE updated their guidance on the management of neuropathic pain in 2013:
first-line treatment*: amitriptyline, duloxetine, gabapentin or pregabalin
if the first-line drug treatment does not work try one of the other 3 drugs
tramadol may be used as ‘rescue therapy’ for exacerbations of neuropathic pain
topical capsaicin may be used for localised neuropathic pain (e.g. post-herpetic neuralgia)
pain management clinics may be useful in patients with resistant problems
*please note that for some specific conditions the guidance may vary. For example carbamazepine is used first-line for trigeminal neuralgia
Neuropathic Pain: Example Question
A 68-year-old man who has a history of Type 2 diabetes for the past 12 years comes to the clinic for review. His diabetes is currently managed with BD mixed insulin and over the past year he has suffered increasing pins and needles and pain in both feet. Apart from Type 2 diabetes, a previous myocardial infarction and intermittent urinary retention over the past year are noted. His GP has diagnosed him with benign prostatic hypertrophy. Examination reveals a blood pressure of 148/82 mmHg, her pulse is 80 beats per minute and regular. There is peripheral neuropathy affecting both feet, which are numb to just below the ankle. Routine bloods including renal function are unremarkable.
Which of the following is the most appropriate intervention?
Amitriptyline Carbamazepine Duloxetine > Pregabalin Tramadol
The correct answer is pregabalin. Pregabalin is a GABA analogue and is recommended as an option by NICE for the treatment of neuropathic pain. it has the advantage versus gabapentin of less frequent daily dosing which drives improved compliance. It is also not associated with urinary retention which drives its selection versus other options listed.
Both amitriptyline and duloxetine are alternative first-line options for the treatment of diabetic neuropathic pain, although they are avoided here because both can be associated with urinary retention. Carbamazepine is not recommended for first-line treatment of diabetic neuropathy, and nor is tramadol because it is only partially effective and has addictive potential.
Brachial Neuritis
Brachial neuritis is characterized by acute onset of unilateral (occasionally bilateral) severe pain, followed by shoulder and scapular weakness several days later. Sensory changes are usually minimal. There may be subsequent rapid wasting of the arm muscles in accordance to which nerve is involved. Precipitating factors include recent trauma, infection, surgery, or even vaccination. Rarely it may be hereditary. The prognosis is usually good except when the phrenic nerve is involved since this can result in significant breathlessness.
Example Question:
A 45 year old male presented with right shoulder pain and weakness. Three weeks ago he had been brought to the emergency department (ER) with the same complaint. The pain was so severe that it awoke him from sleep. At that time he took two paracetamol tablets but that gave him no relief. Eventually the ER team had been forced to give him morphine to relieve his agony having tried less potent analgesia. On further questioning he described the pain as sharp, exacerbated by movement of the shoulder, with numbness at the shoulder tip.
On examination, he was holding his right arm with his left one in adduction and internal rotation. Wasting of the deltoid muscle had been noted. The biceps tendon jerk was absent. Sensations were intact except in a small region over deltoid muscle. Lower limb examination was normal.
One month ago he had a flu. The past medical history was otherwise of no significance.
He admitted to drinking alcohol at least four times a week. He has a ten year old son who is an insulin dependent diabetic.
The following investigations were ordered:
Hb 14 g/dl Platelets 180 * 10^9/l WBC 6 * 10^9/l MCV 85 fl MCH 0.6 fmol/cell MCHC 21 mmol/l Na+ 135 mmol/l K+ 4 mmol/l Creatinine 85 µmol/l Urea 3.2 mmol/l ESR 4 mm/hr ANA negative
What is the most likely diagnosis?
Syringomyelia > Brachial neuritis Adhesive capsulitis Polymyalgia rheumatica Cervical radiculopathy
Adhesive capsulitis usually presents with shoulder pain and restrictions of movement. It would not cause wasting nor neither lower motor neurological signs. Adhesive capsulitis is usually associated with diabetes and thyroid disorders.
Meralgia Paraesthetica
Caused by compression of lateral cutaneous nerve of thigh
Typically burning sensation over anterolateral aspect of thigh
Complex Regional Pain Syndrome
CRPS is the modern, umbrella term for a number of conditions such as reflex sympathetic dystrophy and causalgia.
Describes a number of neurological and related Sx which typically occur following surgery or a minor injury!
CRPS = 3 x more common in women
2 Types:
- Type I = most common - no demonstrable lesion to major nerve
- Type II = lesion to major nerve
Features:
- Progressive disproportionate Sx to original injury/surgery
- Allodynia
- Temp and Skin colour changes
- Oedema and Sweating
- Motor Dysfunction
Mx:
- Early physiotherapy
- Neuropathic analgesia in line with NICE guidance
- Specialist pain team Mx required
Diabetic Neuropathy Mx
Pregabalin is a GABA analogue and is recommended as an option by NICE for the treatment of neuropathic pain. It has the advantage versus gabapentin of less frequent daily dosing which drives improved compliance. Can be used in urinary retention
Both amitriptyline and duloxetine are alternative first-line options for the treatment of diabetic neuropathic pain, but can both be associated with urinary retention.
NB: Carbamazepine is not recommended for first-line treatment of diabetic neuropathy, and nor is tramadol because it is only partially effective and has addictive potential.
